To examine these quantitatively, we need an expression for the Hall emf, Оµ, across a conductor. The Hall effect has other uses that range from the determination of blood flow rate to precision measurement of magnetic field strength. In 1980, it was discovered that the Hall effect is quantized, an example of quantum behavior in a macroscopic object. The Hall effect is used today as a research tool to probe the movement of charges, their drift velocities and densities, and so on, in materials. Historically, the Hall effect was used to show that electrons carry current in metals and it also shows that positive charges carry current in some semiconductors. Note that in Figure 1(b), where positive charges carry the current, the Hall emf has the sign opposite to when negative charges carry the current. One very important use of the Hall effect is to determine whether positive or negative charges carries the current. Thus, if the direction of the field and current are known, the sign of the charge carriers can be determined from the Hall effect. (b) Positive charges moving to the right (conventional current also to the right) are moved to the side, producing a Hall emf of the opposite sign, вЂ“Оµ. The magnetic field is directly out of the page, represented by circled dots it exerts a force on the moving charges, causing a voltage Оµ, the Hall emf, across the conductor. (a) Electrons move to the left in this flat conductor (conventional current to the right).

The creation of a voltage across a current-carrying conductor by a magnetic field is known as the Hall effect, after Edwin Hall, the American physicist who discovered it in 1879.ДЇigure 1. This separation of charge creates a voltage Оµ, known as the Hall emf, across the conductor. Moving electrons feel a magnetic force toward one side of the conductor, leaving a net positive charge on the other side. In part (b), positive charges carry the current and move to the right. In part (a), electrons carry the current and move to the left.

Note that conventional current is to the right in both parts of the figure. The field is perpendicular to the electron drift velocity and to the width of the conductor. Figure 1В shows what happens to charges moving through a conductor in a magnetic field. One result is the Hall effect, which has important implications and applications. The magnetic field also affects charges moving in a conductor. We have seen effects of a magnetic field on free-moving charges. Calculate the Hall emf across a current-carrying conductor.

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